1. Field of the Invention
The present invention relates to a ballast tamping unit for tamping ballast under successive ties of a railroad track, which comprises a frame extending in a longitudinal direction, tamping tool arms mounted on the frame for pivoting about an axis extending perpendicularly to the longitudinal direction, the tamping tool arms having at least one recess at a lower end thereof for receiving and affixing a tamping pick arranged to be immersed in the ballast between two adjacent ties, and a reciprocating drive connected to an upper end of each tamping tool arm for pivoting the tamping tool arm about the axis in the longitudinal direction.
2. Description of the Prior Art
U.S. Pat. No. 4,576,095 discloses a ballast tamping unit of this type, in which the distance between the two tamping tools of a pair of tamping tools reciprocable with respect to each other may be varied. This is necessary particularly when a double tie at a rail joint is to be tamped. To make such a change in the opening width for the tamping tool reciprocation possible, a stop pivotal into engagement with the piston rod of the reciprocating drive may be actuated to change the reciprocating path and thus the opening width. This makes it also possible to make adjustments for varying distances between adjacent ties.
In the tamping of railroad track ties, in which reciprocating tamping picks are immersed in the ballast between adjacent ties, the mutual distance between the successive ties is of great importance. When these distances change in a railroad track, for instance because of a change from wooden to concrete ties, serious problems arise during the ballast tamping operation. Normally, such a change requires the use of another ballast tamping tool unit whose tamping picks are adjusted to the changed distance.
It is the primary object of this invention to provide a ballast tamping unit of the first-described type which simplifies the adaptation to different distances between adjacent ties.
This and other objects are obtained in such a ballast tamping unit when at least one of the tamping tool arms has two of the recesses arranged successively in the longitudinal direction for selectively receiving and affixing the tamping pick.
This simple structural change enables the ballast tamping unit to be retrofitted in a minimum time by removing the tamping pick from one recess and affixing it to the other one of the two recesses in the tamping tool arm. This makes the adaptation to the changed distance between adjacent ties easy. It is particularly advantageous because it enables two railroad track sections with different ties to be tamped without any problem in a single operating pass with the same ballast tamping unit.